The present invention concerns, first of all, a process for placing a piling in the ground, particularly in the ocean floor.
In the ocean, foundations for structures are generally made from inclined or vertical pilings with a large diameter (84" or 2.10 m) built with a diesel pile-driver from the surface, or underwater hydraulic pile-drivers.
In certain types of soil, this solution is not satisfactory, however, and an attempt has been made to replace them with drilled cement pilings. In every case, in the range of actual possibilities, rotational drilling is limited to a maximum diameter of 48" (1.20 m) because the take-up coupling is very large, as is the liquid flow for evacuation of the rubble, with direct circulation. Furthermore, it is difficult to use an extension pipe, and to place a pipe in the borehole for the first meters. Finally, it is impossible to drill at the mouth of the borehole.
It has already been proposed, to overcome these disadvantages, that cutting machines such as those described in the French patent No. 85 14939 and 86 05529 be used. These machines, however, do not allow a pipe to be placed in the borehole along its entire length, and furthermore are not intended to make pilings with a circular cross-section.